函数

Cypher中的函数如果输入参数为null，则返回null。

以字符串作为输入的函数都对Unicode字符进行操作，而不是对标准字符进行操作。例如，size()函数应用于任何Unicode字符将返回1，即使该字符不适合一个字符的16位。

可以通过 SHOW FUNCTIONS 查看函数定义。

函数签名中参数格式：eg：

all(
    variable :: VARIABLE 		//:: VARIABLE，说明是个变量，可用于后面的 WHERE 部分
	IN 
list :: LIST OF ANY? 			//list，是个LIST泛型。
WHERE predicate :: ANY?			// predicate，是任意的断言
) 
:: (BOOLEAN?)					//函数返回值类型为BOOLEAN

断言函数

Function	Signature	Description
`all()`	`all(variable :: VARIABLE IN list :: LIST OF ANY? WHERE predicate :: ANY?) :: (BOOLEAN?)`	Returns true if the predicate holds for all elements in the given list.
`any()`	`any(variable :: VARIABLE IN list :: LIST OF ANY? WHERE predicate :: ANY?) :: (BOOLEAN?)`	Returns true if the predicate holds for at least one element in the given list.
`exists()`	`exists(input :: ANY?) :: (BOOLEAN?)`	Returns `true` if a match for the pattern exists in the graph.
`isEmpty()`	`isEmpty(input :: LIST? OF ANY?) :: (BOOLEAN?)`	Checks whether a list is empty.
`isEmpty()`	`isEmpty(input :: MAP?) :: (BOOLEAN?)`	Checks whether a map is empty.
`isEmpty()`	`isEmpty(input :: STRING?) :: (BOOLEAN?)`	Checks whether a string is empty.
`none()`	`none(variable :: VARIABLE IN list :: LIST OF ANY? WHERE predicate :: ANY?) :: (BOOLEAN?)`	Returns true if the predicate holds for no element in the given list.
`single()`	`single(variable :: VARIABLE IN list :: LIST OF ANY? WHERE predicate :: ANY?) :: (BOOLEAN?)`	Returns true if the predicate holds for exactly one of the elements in the given list.

标量函数

Function	Signature	Description
`coalesce()`	`coalesce(input :: ANY?) :: (ANY?)`	返回第一个非null值。
`endNode()`	`endNode(input :: RELATIONSHIP?) :: (NODE?)`	Returns the end node of a relationship.
`head()`	`head(list :: LIST? OF ANY?) :: (ANY?)`	Returns the first element in a list.
`id()`	`id(input :: NODE?) :: (INTEGER?)`	Deprecated Returns the id of a node. Replaced by `elementId()`
	`id(input :: RELATIONSHIP?) :: (INTEGER?)`	Deprecated Returns the id of a relationship. Replaced by `elementId()`.
`last()`	`last(list :: LIST? OF ANY?) :: (ANY?)`
`length()`	`length(input :: PATH?) :: (INTEGER?)`	Returns the length of a path.
`properties()`	`properties(input :: MAP?) :: (MAP?)`	返回一个对象的所有属性，作为一个map
	`properties(input :: NODE?) :: (MAP?)`	返回一个节点的所有属性，作为一个map
	`properties(input :: RELATIONSHIP?) :: (MAP?)`	返回一个关系的所有属性，作为一个map
`randomUUID()`	`randomUUID() :: (STRING?)`
`size()`	`size(input :: LIST? OF ANY?) :: (INTEGER?)`	Returns the number of items in a list.
	`size(input :: STRING?) :: (INTEGER?)`	Returns the number of Unicode characters in a string.
`startNode()`	`startNode(input :: RELATIONSHIP?) :: (NODE?)`
`toBoolean()`	`toBoolean(input :: STRING?) :: (BOOLEAN?)`
	`toBoolean(input :: BOOLEAN?) :: (BOOLEAN?)`
	`toBoolean(input :: INTEGER?) :: (BOOLEAN?)`
`toBooleanOrNull()`	`toBooleanOrNull(input :: ANY?) :: (BOOLEAN?)`	转换为boolean，不能转换返回null。
`toFloat()`	`toFloat(input :: NUMBER?) :: (FLOAT?)`
	`toFloat(input :: STRING?) :: (FLOAT?)`
`toFloatOrNull()`	`toFloatOrNull(input :: ANY?) :: (FLOAT?)`	转换为小数，不能转换返回null。
`toInteger()`	`toInteger(input :: NUMBER?) :: (INTEGER?)`
	`toInteger(input :: BOOLEAN?) :: (INTEGER?)`
	`toInteger(input :: STRING?) :: (INTEGER?)`
`toIntegerOrNull()`	`toIntegerOrNull(input :: ANY?) :: (INTEGER?)`	转换为整形，不能转换返回null。
`type()`	`type(input :: RELATIONSHIP?) :: (STRING?)`	Returns the string representation of the relationship type.

示例

CREATE (p:Person {name: 'Stefan', city: 'Berlin'})
RETURN properties(p)
//OUT PUT:
//: {"city":"Berlin","name":"Stefan"}

聚合函数

Function	Signature	Description
`avg()`	`avg(input :: DURATION?) :: (DURATION?)`
	`avg(input :: FLOAT?) :: (FLOAT?)`
	`avg(input :: INTEGER?) :: (INTEGER?)`
`collect()`	`collect(input :: ANY?) :: (LIST? OF ANY?)`	收集数据作为一个LIST。
`count()`	`count(input :: ANY?) :: (INTEGER?)`
`max()`	`max(input :: ANY?) :: (ANY?)`
`min()`	`min(input :: ANY?) :: (ANY?)`
`percentileCont()`	`percentileCont(input :: FLOAT?, percentile :: FLOAT?) :: (FLOAT?)`
`percentileDisc()`	`percentileDisc(input :: FLOAT?, percentile :: FLOAT?) :: (FLOAT?)`
	`percentileDisc(input :: INTEGER?, percentile :: FLOAT?) :: (INTEGER?)
`stdev()`	`stdev(input :: FLOAT?) :: (FLOAT?)`
`stdevp()`	`stdevp(input :: FLOAT?) :: (FLOAT?)`
`sum()`	`sum(input :: DURATION?) :: (DURATION?)`
	`sum(input :: FLOAT?) :: (FLOAT?)
	`sum(input :: INTEGER?) :: (INTEGER?)

集合函数

Function	Signature	Description
`keys()`	`keys(input :: MAP?) :: (LIST? OF STRING?)`	返回MAP的所有KEY LIST
	`keys(input :: NODE?) :: (LIST? OF STRING?)`	返回节点的所有属性 LIST
	`keys(input :: RELATIONSHIP?) :: (LIST? OF STRING?)`	返回关系的所有属性 LIST
`labels()`	`labels(input :: NODE?) :: (LIST? OF STRING?)`	Returns a list containing the string representations for all the labels of a node.
`nodes()`	`nodes(input :: PATH?) :: (LIST? OF NODE?)`	Returns a list containing all the nodes in a path.
`range()`	`range(start :: INTEGER?, end :: INTEGER?) :: (LIST? OF INTEGER?)`	Returns a list comprising all integer values within a specified range.
	`range(start :: INTEGER?, end :: INTEGER?, step :: INTEGER?) :: (LIST? OF INTEGER?)`	Returns a list comprising all integer values within a specified range created with step length.
`reduce()`	`reduce(accumulator :: VARIABLE = initial :: ANY?, variable :: VARIABLE IN list :: LIST OF ANY?	expression :: ANY) :: (ANY?)`
`relationships()`	`relationships(input :: PATH?) :: (LIST? OF RELATIONSHIP?)`	Returns a list containing all the relationships in a path.
`reverse()`	`reverse(input :: LIST? OF ANY?) :: (LIST? OF ANY?)`	Returns a list in which the order of all elements in the original list have been reversed.
`tail()`	`tail(input :: LIST? OF ANY?) :: (LIST? OF ANY?)`	Returns all but the first element in a list.
`toBooleanList()`	`toBooleanList(input :: LIST? OF ANY?) :: (LIST? OF BOOLEAN?)`
`toFloatList()`	`toFloatList(input :: LIST? OF ANY?) :: (LIST? OF FLOAT?)`
`toIntegerList()`	`toIntegerList(input :: LIST? OF ANY?) :: (LIST? OF INTEGER?)`
`toStringList()`	`toStringList(input :: LIST? OF ANY?) :: (LIST? OF STRING?)`

示例

toBooleanList()：

RETURN toBooleanList(null) as noList,
toBooleanList([null, null]) as nullsInList,
toBooleanList(['a string', true, 'false', null, ['A','B']]) as mixedList

noList	nullsInList	mixedList
`<null>`	`[<null>,<null>]`	`[<null>,true,false,<null>,<null>]`

总结：

参数不是个LIST，报错
LIST 中的null，不转换，保留
LIST中的不可转换元素，结果为null。
BOOLEAN类型的元素，保留原始值

数值函数

Function	Signature	Description
`abs()`	`abs(input :: FLOAT?) :: (FLOAT?)`
	`abs(input :: INTEGER?) :: (INTEGER?)`
`ceil()`	`ceil(input :: FLOAT?) :: (FLOAT?)`
`floor()`	`floor(input :: FLOAT?) :: (FLOAT?)`
`isNaN()`	`isNaN(input :: FLOAT?) :: (BOOLEAN?)`	Returns `true` if the floating point number is `NaN`.
	`isNaN(input :: INTEGER?) :: (BOOLEAN?)`
`rand()`	`rand() :: (FLOAT?)`
`round()`	`round(input :: FLOAT?) :: (FLOAT?)`
	`round(value :: FLOAT?, precision :: NUMBER?) :: (FLOAT?)`
	`round(value :: FLOAT?, precision :: NUMBER?, mode :: STRING?) :: (FLOAT?)`
`sign()`	`sign(input :: FLOAT?) :: (INTEGER?)`
	`sign(input :: INTEGER?) :: (INTEGER?)`

对数函数

Function	Signature	Description
`e()`	`e() :: (FLOAT?)`	返回e。
`exp()`	`exp(input :: FLOAT?) :: (FLOAT?)`	返回e^n。
`log()`	`log(input :: FLOAT?) :: (FLOAT?)`	返回自然对数，以e为底
`log10()`	`log10(input :: FLOAT?) :: (FLOAT?)`	返回以10位底的对数
`sqrt()`	`sqrt(input :: FLOAT?) :: (FLOAT?)`	平方差

三角函数

Function	Signature	Description
`acos()`	`acos(input :: FLOAT?) :: (FLOAT?)`
`asin()`	`asin(input :: FLOAT?) :: (FLOAT?)
`atan()`	`atan(input :: FLOAT?) :: (FLOAT?)`
`atan2()`	`atan2(y :: FLOAT?, x :: FLOAT?) :: (FLOAT?)`
`cos()`	`cos(input :: FLOAT?) :: (FLOAT?)`
`cot()`	`cot(input :: FLOAT?) :: (FLOAT?)`
`degrees()`	`degrees(input :: FLOAT?) :: (FLOAT?)`	将弧度转换为角度
`haversin()`	`haversin(input :: FLOAT?) :: (FLOAT?)`	半正矢计算
`pi()`	`pi() :: (FLOAT?)`
`radians()`	`radians(input :: FLOAT?) :: (FLOAT?)`	将角度转换为弧度
`sin()`	`sin(input :: FLOAT?) :: (FLOAT?)`
`tan()`	`tan(input :: FLOAT?) :: (FLOAT?)`

字符串函数

Function	Signature	Description
`left()`	`left(original :: STRING?, length :: INTEGER?) :: (STRING?)`
`ltrim()`	`ltrim(input :: STRING?) :: (STRING?)`
`replace()`	`replace(original :: STRING?, search :: STRING?, replace :: STRING?) :: (STRING?)`
`reverse()`	`reverse(input :: STRING?) :: (STRING?)`
`right()`	`right(original :: STRING?, length :: INTEGER?) :: (STRING?)
`rtrim()`	`rtrim(input :: STRING?) :: (STRING?)`
`split()`	`split(original :: STRING?, splitDelimiter :: STRING?) :: (LIST? OF STRING?)`
	`split(original :: STRING?, splitDelimiters :: LIST? OF STRING?) :: (LIST? OF STRING?)`
`substring()`	`substring(original :: STRING?, start :: INTEGER?) :: (STRING?)`	从0开始
	`substring(original :: STRING?, start :: INTEGER?, length :: INTEGER?) :: (STRING?)`
`toLower()`	`toLower(input :: STRING?) :: (STRING?)`
`toString()`	`toString(input :: ANY?) :: (STRING?)`
`toStringOrNull()`	`toStringOrNull(input :: ANY?) :: (STRING?)`
`toUpper()`	`toUpper(input :: STRING?) :: (STRING?)`
`trim()`	`trim(input :: STRING?) :: (STRING?)`

时间函数

Function	Signature	Description
`date()`	`date(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATE?)`	创建DATE
`date.realtime()`	`date.realtime(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATE?)`	使用 realtime clock 创建当前DATE
`date.statement()`	`date.statement(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATE?)`	使用 statement clock 创建当前DATE
`date.transaction()`	`date.transaction(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATE?)`	使用 transaction clock 创建当前DATE
`date.truncate()`	`date.truncate(unit :: STRING?, input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?, fields = null :: MAP?) :: (DATE?)`	截断DATE
`datetime()`	`datetime(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATETIME?)`
`datetime.fromepoch()`	`datetime.fromepoch(seconds :: NUMBER?, nanoseconds :: NUMBER?) :: (DATETIME?)`
`datetime.fromepochmillis()`	`datetime.fromepochmillis(milliseconds :: NUMBER?) :: (DATETIME?)`
`datetime.realtime()`	`datetime.realtime(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATETIME?)`
`datetime.statement()`	`datetime.statement(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATETIME?)`
`datetime.transaction()`	`datetime.transaction(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (DATETIME?)`
`datetime.truncate()`	`datetime.truncate(unit :: STRING?, input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?, fields = null :: MAP?) :: (DATETIME?)`
`localdatetime()`	`localdatetime(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALDATETIME?)`
`localdatetime.realtime()`	`localdatetime.realtime(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALDATETIME?)`
`localdatetime.statement()`	`localdatetime.statement(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALDATETIME?)`
`localdatetime.transaction()`	`localdatetime.transaction(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALDATETIME?)`
`localdatetime.truncate()`	`localdatetime.truncate(unit :: STRING?, input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?, fields = null :: MAP?) :: (LOCALDATETIME?)`
`localtime()`	`localtime(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALTIME?)`
`localtime.realtime()`	`localtime.realtime(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALTIME?)`
`localtime.statement()`	`localtime.statement(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALTIME?)`
`localtime.transaction()`	`localtime.transaction(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (LOCALTIME?)`
`localtime.truncate()`	`localtime.truncate(unit :: STRING?, input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?, fields = null :: MAP?) :: (LOCALTIME?)`
`time()`	`time(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (TIME?)`
`time.realtime()`	`time.realtime(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (TIME?)`
`time.statement()`	`time.statement(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (TIME?)`
`time.transaction()`	`time.transaction(timezone = DEFAULT_TEMPORAL_ARGUMENT :: ANY?) :: (TIME?)`
`time.truncate()`	`time.truncate(unit :: STRING?, input = DEFAULT_TEMPORAL_ARGUMENT :: ANY?, fields = null :: MAP?) :: (TIME?)`

时钟控制

transaction: 同一个事务，时间返回相同值。
statement: 同一个语句的同一次调用，时间返回相同值。
realtime: 系统时间。

截断单位

millennium:千年
century:世纪
decade:十年
year:
weekYear:
quarter:
month:
week:
day:
hour:
minute:
second:
millisecond: 毫秒
microsecond: 微秒

示例

date([{timezone}])
RETURN date() AS currentDate
RETURN date({timezone: 'America/Los Angeles'}) AS currentDateInLA

date({year [, month, day]})
UNWIND [
date({year: 1984, month: 10, day: 11}),
date({year: 1984, month: 10}),
date({year: 1984})
] AS theDate
RETURN theDate

date({year [, week, dayOfWeek]})
UNWIND [
date({year: 1984, week: 10, dayOfWeek: 3}),
date({year: 1984, week: 10}),
date({year: 1984})
] AS theDate
RETURN theDate

duration函数

Function	Signature	Description
`duration()`	`duration(input :: ANY?) :: (DURATION?)`
`duration.between()`	`duration.between(from :: ANY?, to :: ANY?) :: (DURATION?)`	计算2个时间差
`duration.inDays()`	`duration.inDays(from :: ANY?, to :: ANY?) :: (DURATION?)`
`duration.inMonths()`	`duration.inMonths(from :: ANY?, to :: ANY?) :: (DURATION?)`
`duration.inSeconds()`	`duration.inSeconds(from :: ANY?, to :: ANY?) :: (DURATION?)`

示例

duration([ {years, quarters, months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds} ])
            
duration(temporalAmount)   // temporalAmount STRING类型

duration标准字符串格式：P[nY][nM][nW][nD][T[nH][nM][nS]]，具体见：https://neo4j.com/docs/cypher-manual/current/values-and-types/temporal/#cypher-temporal-specifying-durations

duration.between(instant1, instant2)

字段

years
quarters
months
weeks
days
hours
minutes
seconds
milliseconds
microseconds
nanoseconds

空间函数

Function	Signature	Description
`point.distance()`	`point.distance(from :: POINT?, to :: POINT?) :: (FLOAT?)
`point()` - Cartesian 2D	`point(input :: MAP?) :: (POINT?)`
`point()` - Cartesian 3D	`point(input :: MAP?) :: (POINT?)`
`point()` - WGS 84 2D	`point(input :: MAP?) :: (POINT?)
`point()` - WGS 84 3D	`point(input :: MAP?) :: (POINT?)
`point.withinBBox()`	`point.withinBBox(point :: POINT?, lowerLeft :: POINT?, upperRight :: POINT?) :: (BOOLEAN?)`

加载 CSV 函数

Function	Signature	Description
`file()`	`file() :: (STRING?)`	返回文件路径
`linenumber()`	`linenumber() :: (INTEGER?)`	返回行数

Graph functions

Function	Signature	Description
`graph.names()`	`graph.names() :: (LIST? OF STRING?)`
`graph.propertiesByName()`	`graph.propertiesByName(name :: STRING?) :: (MAP?)`
`graph.byName()`	`USE graph.byName(name :: STRING?)`

用户自定义函数

Type	Description	Usage	Developing
Scalar	For each row the function takes parameters and returns a result.	Using UDF	Extending Neo4j (UDF)
Aggregating	Consumes many rows and produces an aggregated result.	Using aggregating UDF	Extending Neo4j (Aggregating UDF)